First Study of the

New astronomical observations point to a nucleosynthesis picture that goes beyond what was accepted until recently. The intermediate "i" process was proposed as a plausible scenario to explain some of the unusual abundance patterns observed in metal-poor stars. The most important nuclear physics properties entering i-process calculations are the neutron-capture cross sections and they are almost exclusively not known experimentally. Here we provide the first experimental constraints on the ^{139}Ba(n,γ)^{140}Ba reaction rate, which is the dominant source of uncertainty for the production of lanthanum, a key indicator of i-process conditions. This is an important step towards identifying the exact astrophysical site of stars carrying the i-process signature.

Accuracy of WatchPAT for the Diagnosis of Obstructive Sleep Apnea in Patients with Chronic Obstructive Pulmonary Disease.

The co-existence of chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA), termed the overlap syndrome (OVS), is associated with adverse outcomes that may be reversed with treatment. However, diagnosis is limited by the apparent need for in-laboratory polysomnography (PSG). WatchPAT is a portable diagnostic device that is validated for the diagnosis of OSA that might represent an attractive tool for the diagnosis of OVS.Subjects with established COPD were recruited from a general population. Subjects underwent PSG and simultaneous recording with WatchPAT. Pulmonary function testing and questionnaires were also performed.A total of 36 subjects were recruited and valid data was obtained on 33 (age 63 ± 7, BMI 28 ± 7, 61% male, FEV1 56 ± 20% predicted). There was no significant difference in the apnea-hypopnea index (AHI) between PSG and WatchPAT (19 ± 20 versus 20 ± 15 events/h; mean difference 2(-2, 5) events/h; p = 0.381). The AHI was not significantly different in rapid eye movement (REM) and non-rapid eye movement (NREM) determined by PSG versus REM and NREM determined by WatchPAT. WatchPAT slightly overestimated total and REM sleep time, and sleep efficiency. The sensitivity of WatchPAT at an AHI cut-off of ≥5, ≥15, and ≥30 events/h for corresponding PSG AHI cut-offs was 95.8, 92.3, and 88.9, respectively; specificity was 55, 65.0, and 95.8, respectively.WatchPAT is able to determine OSA reliably in patients with COPD. The availability of this additional diagnostic modality may lead to improved detection of OVS, which may in turn lead to improved outcomes for a group of COPD patients at high risk of poor outcomes.

Electrochemical Synthesis of Novel Zn-Doped TiO2 Nanotube/ZnO Nanoflake Heterostructure with Enhanced DSSC Efficiency.

ABSTRACT: The paper reports the fabrication of Zn-doped TiO2 nanotubes (Zn-TONT)/ZnO nanoflakes heterostructure for the first time, which shows improved performance as a photoanode in dye-sensitized solar cell (DSSC). The layered structure of this novel nanoporous structure has been analyzed unambiguously by Rutherford backscattering spectroscopy, scanning electron microscopy, and X-ray diffractometer. The cell using the heterostructure as photoanode manifests an enhancement of about an order in the magnitude of the short circuit current and a seven-fold increase in efficiency, over pure TiO2 photoanodes. Characterizations further reveal that the Zn-TONT is preferentially oriented in [001] direction and there is a Ti metal-depleted interface layer which leads to better band alignment in DSSC.

Pilot study of the effects of bariatric surgery and continuous positive airway pressure treatment on vascular function in obese subjects with obstructive sleep apnoea.

BACKGROUND: The mechanisms by which obesity and obstructive sleep apnoea (OSA) may contribute to endothelial dysfunction are unclear. AIMS: We sought to follow up a sample of obese subjects undergoing either bariatric surgery or continuous positive airway pressure (CPAP) therapy to treat OSA. We hypothesised improved vascular function with both therapeutic approaches, consistent with a reversible OSA effect on the circulation. METHODS: Twenty-seven obese (BMI ≥30 kg/m(2)) subjects with OSA underwent either bariatric surgery without CPAP (n = 12, median BMI 43.7 kg/m(2) IQR 9.4) or CPAP (n = 15, median BMI 33.8 kg/m(2) IQR 6.6). Polysomnography and vascular testing (flow-mediated dilation of the brachial artery measured with high-resolution ultrasound, endothelium-dependent change in skin blood flow measured with laser Doppler flowmetry, and arterial stiffness measured with applanation tonometry) took place at baseline and after 6 months. RESULTS: Both groups showed significant improvements in the apnoea-hypopnea index and overnight oxygen saturation. Endothelium-dependent microvascular reactivity was 45.6% (IQR 37.5) at baseline in the CPAP group, which increased to 69.1% (IQR 62.3) post-treatment (P < 0.05). No significant changes were observed in the surgery group, despite significant weight loss (post-surgery BMI 32.7 kg/m2 IQR 8.6 (P < 0.01); no change in BMI was observed in the CPAP group. There were no significant changes in brachial artery flow-mediated dilation in either group. CONCLUSIONS: This pilot study demonstrates that 6 months of CPAP may be sufficient to improve endothelium-dependent microvascular reactivity, while substantial surgically induced weight loss did not result in improvements. Further research should be directed towards comparative effectiveness trials using these novel surrogate outcomes, as well as hard cardiovascular outcomes.

The effect of lung stretch during sleep on airway mechanics in overweight and obese asthma.

Both obesity and sleep reduce lung volume and limit deep breaths, possibly contributing to asthma. We hypothesize that increasing lung volume dynamically during sleep would reduce airway resistance in asthma. Asthma (n=10) and control (n=10) subjects were studied during sleep at baseline and with increased lung volume via bi-level positive airway pressure (BPAP). Using forced oscillations, respiratory system resistance (R(rs)) and reactance (X(rs)) were measured during sleep and R(rs) was partitioned to upper and lower airway resistance (R(up), R(low)) using an epiglottic pressure catheter. R(rs) and R(up) increased with sleep (p<0.01) and X(rs) was decreased in REM (p=0.02) as compared to wake. R(rs), R(up), and R(low), were larger (p<0.01) and X(rs) was decreased (p<0.02) in asthma. On BPAP, R(rs) and R(up) were decreased (p<0.001) and X(rs) increased (p<0.01), but R(low) was unchanged. High R(up) was observed in asthma, which reduced with BPAP. We conclude that the upper airway is a major component of R(rs) and larger lung volume changes may be required to alter R(low).

Study of two-neutron radioactivity in the decay of 26O.

A new technique was developed to measure the lifetimes of neutron unbound nuclei in the picosecond range. The decay of 26O→24O+n+n was examined as it had been predicted to have an appreciable lifetime due to the unique structure of the neutron-rich oxygen isotopes. The half-life of 26O was extracted as 4.5(-1.5)(+1.1)(stat)±3(syst) ps. This corresponds to 26O having a finite lifetime at an 82% confidence level and, thus, suggests the possibility of two-neutron radioactivity.

Evidence for the ground-state resonance of 26O.

Evidence for the ground state of the neutron-unbound nucleus (26)O was observed for the first time in the single proton-knockout reaction from a 82 MeV/u (27)F beam. Neutrons were measured in coincidence with (24)O fragments. (26)O was determined to be unbound by 150(-150)(+50) keV from the observation of low-energy neutrons. This result agrees with recent shell-model calculations based on microscopic two- and three-nucleon forces.

First observation of ground state dineutron decay: 16Be.

We report on the first observation of dineutron emission in the decay of 16Be. A single-proton knockout reaction from a 53 MeV/u 17B beam was used to populate the ground state of 16Be. 16Be is bound with respect to the emission of one neutron and unbound to two-neutron emission. The dineutron character of the decay is evidenced by a small emission angle between the two neutrons. The two-neutron separation energy of 16Be was measured to be 1.35(10) MeV, in good agreement with shell model calculations, using standard interactions for this mass region.

Exploring the low-Z shore of the island of inversion at n=19.

The technique of invariant mass spectroscopy has been used to measure, for the first time, the ground state energy of neutron-unbound (28)F, determined to be a resonance in the (27)F+n continuum at 220(50) keV. States in (28)F were populated by the reactions of a 62 MeV/u (29)Ne beam impinging on a 288 mg/cm(2) beryllium target. The measured (28)F ground state energy is in good agreement with USDA/USDB shell model predictions, indicating that pf shell intruder configurations play only a small role in the ground state structure of (28)F and establishing a low-Z boundary of the island of inversion for N=19 isotones.

Unresolved question of the 10He ground state resonance.

The ground state of (10)He was populated using a 2p2n-removal reaction from a 59 MeV/u (14)Be beam. The decay energy of the three-body system, (8)He+n+n, was measured and a resonance was observed at E=1.60(25) MeV with a 1.8(4) MeV width. This result is in agreement with previous invariant mass spectroscopy measurements, using the (11)Li(-p) reaction, but is inconsistent with recent transfer reaction results. The proposed explanation that the difference, about 500 keV, is due to the effect of the extended halo nature of (11)Li in the one-proton knockout reaction is no longer valid as the present work demonstrates that the discrepancy between the transfer reaction results persists despite using a very different reaction mechanism, (14)Be(-2p2n).

Near-barrier fusion of the 8B + 58Ni proton-halo system.

Fusion cross sections were measured for the exotic proton-halo nucleus 8B incident on a 58Ni target at several energies near the Coulomb barrier. This is the first experiment to report on the fusion of a proton-halo nucleus. The resulting excitation function shows a striking enhancement with respect to expectations for normal projectiles. Evidence is presented that the sum of the fusion and breakup yields saturates the total reaction cross section.

Determination of the N=16 shell closure at the oxygen drip line.

The neutron unbound ground state of (25)O (Z=8, N=17) was observed for the first time in a proton knockout reaction from a (26)F beam. A single resonance was found in the invariant mass spectrum corresponding to a neutron decay energy of 770_+20(-10) keV with a total width of 172(30) keV. The N=16 shell gap was established to be 4.86(13) MeV by the energy difference between the nu1s(1/2) and nu0d(3/2) orbitals. The neutron separation energies for (25)O agree with the calculations of the universal sd shell model interaction. This interaction incorrectly predicts an (26)O ground state that is bound to two-neutron decay by 1 MeV, leading to a discrepancy between the theoretical calculations and experiment as to the particle stability of (26)O. The observed decay width was found to be on the order of a factor of 2 larger than the calculated single-particle width using a Woods-Saxon potential.

Selective population and neutron decay of an excited state of 23O.

We have observed a resonance in neutron-fragment coincidence measurements that is presumably the first excited state of 23O at 2.8(1) MeV excitation energy which decays into the ground state of 22O. This interpretation is consistent with theory. The reaction mechanism supports the assignment of the observed state as the 5/2+ hole state. This assignment and the recently observed 3/2+ particle state advance the understanding of 23O.

Doppler shift as a tool for studies of isobaric analog states of neutron-rich nuclei: application to 7He.

We have developed a new technique to study exotic neutron-rich nuclei via their isobaric analog states (IAS). We populate high-isospin states in resonant reactions of radioactive ion beams with protons. Characteristic gamma rays emitted from excited decay products were used to identify the population of the IAS. We show that information on the differential and total cross section for formation of the IAS can be extracted from the energy spectrum of the Doppler-shifted gamma rays. This technique was applied to the study of T=3/2 states in 7Li, which are analogs of states in 7He. The analog of the 7He ground state was clearly observed, whereas the presence of the analog of a narrow 1/2(-) state at 0.6 MeV excitation in 7He reported by M. Meister et al. [Phys. Rev. Lett. 88, 102501 (2002)] was excluded at the 90% confidence level. Evidence is presented for a broad 1/2(-) state at a higher excitation energy in 7He.

Analog states of 7He observed via the 6He(p,n) reaction.

Isobaric analog states of 7He have been investigated by a novel technique involving the observation of the resonant yield of neutrons from the 6He(p,n) reaction in coincidence with gamma rays from the decay of the (0(+),T=1) state in 6Li. The gamma rays provide a clean signature for the isospin-conserving neutron decay of the low-lying isobaric analog resonances. It is conclusively shown that the analog of the recently observed low-lying spin-orbit partner of the 7He ground state does not exist. Evidence is presented that this state lies at much higher energies, in agreement with microscopic calculations.

New approach for measuring properties of rp-process nuclei.

A new experimental approach was developed that can reduce the uncertainties in astrophysical rapid proton capture (rp) process calculations due to nuclear data. This approach utilizes neutron removal from a radioactive ion beam to populate the nuclear states of interest. Excited states were deduced by the gamma-decay spectra measured in a semiconductor Ge-detector array. In the first case studied, 33Ar, excited states were measured with uncertainties of several keV. The 2 orders of magnitude improvement in the uncertainty of the level energies resulted in a 3 orders of magnitude improvement in the uncertainty of the calculated 32Cl(p,gamma)33Ar rate that is critical to the modeling of the rp process. This approach has the potential to measure key properties of almost all interesting nuclei on the rp-process path.